Guanidine naphthenates and process for making them



United States Patent 3,142,636 GUANIDWE NAPHTHENATES AND PROCESS FORMAKING THEM Allen F. Millikan, Crystal Lake, 111., assignor to The PureOil Company, Chicago, 111., a corporation of Ohio No Drawing. Filed July13, I961, Ser. No. 123,639 13 Claims. (Cl. 208-'180) This inventionrelates to new and useful improvements in processes for the refining ofcrude petroleum fractions to reduce the amount of naphthenic acidspresent therein, and to novel naphthenate salts produced in the refiningprocess.

Many crude oils contain sufiicient quantities of naphthenic acids tomake it necessary to modify refining procedures in order that productssuch as lubricating stocks and lubricating oils be essentially free ofacids. In the refining of crude petroleum which contains substantialamounts of naphthenic acids, there is a problem of excessive corrosionin the distillation equipment due to the production of hydrogen chlorideby reaction of naphthenic acids in the petroleum with trace amounts ofinorganic chlorides in solution. In the past, attempts have been made toremove naphthenic acids from crude petroleum or from petroleum fractionsat various points in the refining processes, or to convert thenaphthenic acids into salts or esters. Prior methods dealing withnaphthenic acids have included neutralization by alkali, esterification,catalytic decarboxylation of the acids, extraction with various phenols,alcohols, or other solvents, with or without neutralization, and claytreating. Numerous countercurrent solvent extraction processes have beenproposed for use in refining petroleum oils. One process which has beenused utilizes an extracting solution consisting of an alkylolaminedissolved in an aliphatic alcohol to react with and remove thenaphthenic acids. Other methods have utilized esterification reagents toconvert naphthenic acids into neutral esters which are left in the oil.Still another method which has been used for reducing the acidity ofcrude petroleum and petroleum fractions has utilized treatment withaqueous alkali to neutralize naphthenic acids, followed by separation ofthe aqueous solution of alkali metal and naphthenate salts. Thisprocess, however, has been ineffective with many types of petroleum andpetroleum fractions which contain high-molecular-weight naphthenicacids, because the corresponding alkali metal naphthenates arepreferentially oil-soluble and cannot be removed by Washing with wateror alcohol.

It is therefore one object of this invention to provide an improvedprocess for reducing the acid neutralization number of crude petroleumand petroleum fractions containing substantial amounts of naphthenicacids which form alkali metal salts which are oil-soluble.

.Another object of this invention is to provide an improved process forrefining crude petroleum and petroleum fractions containing substantialamounts of naphthenic acids in which the naphthenic acids are convertedinto guanidine or substituted-guanidine salts which can be extracted inalcohol or aqueous alcohol solution.

Another object of this invention is to provide a novel class ofnaphthenate salts.

A feature of this invention is the provision of an improved process forrefining crude petroleum, or a petroleum fraction containing substantialamounts of mph ice thenic acids, by treatment with a guanidine compoundto produce a mixture of guanidine or substituted-guanidine naphthenateswhich are removed by extraction with alcohol or aqueous alcoholmixtures.

Another feature of this invention is the provision of an improvedprocess for the refining of petroleum fractions which comprises mixingand heating the fraction with a slurry or solution of a guanidinecompound in aqueous alcohol and removal of the resulting guanidine (orsubstituted-guanidine) naphthenates in the form of alcoholic solution.

Another feature of this invention is the provision of an improvedprocess for reclaiming used crankcase oils in which the used oil istreated with a solid adsorbent to remove asphaltic and tarry materials,and then is treated with a guanidine compound to remove acidic materialspresent in the oil.

Still another feature of this invention is the provision of a novelclass of naphthenate salts of guanidine andalkyl-substituted-guanidines.

Other objects and features of this invention will become apparent fromtime to time throughout the specification and claims as hereinafterrelated.

This invention is based upon my discovery that naphthenic acids can beremoved from crude petroleum or petroleum fractions by treatment withguanidine, substituted-guanidines, or salts (of weak acids) thereof. Theguanidine or substituted-guanidine salts which are formed are removed byextraction with an alcohol or aqueous alcohol solution. .It is wellknown that naphthenic acids present in crude oil, and in petroleumfractions such as lubricating oils and lubricating oil extracts, are notreadily removable by washing the oils with aqueous alkali solutions. Infact, these alkali naphthenates are soluble in oils to a much greaterextent than they are in water. Since the acid neutralization number ofcrude oil and petroleum fractions is due largely to the presence ofnaphthenic acids, washing the oil with aqueous alkali solution is oflittle use for reducing the acid neutralization number. I have foundthat the treatment of petroleum fractions containing naphthenic acidswith guanidine compounds selected from the group consisting ofguanidine, alkyl-substituted guanidines, and salts (of weak acids)thereof in alcohol or aqueous-alcohol solution (or slurry) converts thenaphthenic acids into guanidine (or substituted guanidine) naphthenateswhich are readily removed by alcohol or aqueous-alcohol solutions. Inaddition, the guanidine or substituted-guanidine naphthenates which arerecovered are novel compounds which are useful for a variety ofpurposes. The guanidine and substituted-guanidine naphthenates areuseful as detergents, per se, or in solution in oils, and are useful inincreasing the resistance of lubricating oils to wear and produce aslight improvement in octane number when mixed with gasolines.

In carrying out this process, sufiicient guanidine, alkylsubstitutedguanidine, or salts thereof, is added in solution in alcohol or aqueousalcohol (or any other suitable inert solvent) to neutralize thenaphthenic acids present in the crude oil or petroleum fraction. Whenoil-soluble guanidine compounds are used to react with the naphthenicacids, it is sufficient to use stoichiometric amounts of the reactant.When oil-insoluble salts of guanidine (or substituted guanidines) areused, the amount of the reactant should be greater than stoichiometricbecause of the relative inefficiency of contact. In either case, it isdesirable to agitate the reaction mixture to obtain intimate contactbetween the guanidine compound and the naphthenic acids. While guanidineis very eifective in this process, its instability and the difficultiesassociated with its handling make it less suitable than certainderivatives. In carrying out this process, guanidine can be usedalthough guanidine salts of weak acids such as guanidine carbonate,guanidine acetate, guanidine borate, etc., are preferred. Of these, thecarbonate is preferred since the carbonic acid formed breaks up into COand H 0, whereas other acids may leave undesirable residues. Likewise,substituted guanidines, preferably alkyl-substituted guanidines, such asmethylguanidine, dimethylguanidine, tetramethylguanidine,ethylguanidine, tetraethylguanidine, tetrapropylguanidine,tetraoctylguanidine, etc., are also preferred because of theirsolubility in petroleum fractions which makes the reaction withnaphthenic acids more efficient. The weak-acid salts of thesesubstitutedguanidines can also be used in the process. Where guanidineor substituted-guanidine salts are used as reactants, it is generallynecessary to heat the reaction mixture and agitate the same in order toeffect a decomposition reaction in which the guanidine orsubstitutedguanidine naphthenate is formed as a product. The guanidineor substituted-guanidine naphthenates which are obtained in this mannerare generally oil-insoluble, but are somewhat soluble in water andaqueous alcohol solutions.

Where this process is used for reducing the acid neutralization numberof a crude oil, the treatment is preferably carried out prior todesalting the crude so that the aqueous-alcohol layer containing thewater-soluble guanidine (or substituted-guanidine) naphthenate can beremoved in the desalter. When this process is used in the treatment ofrefined petroleum fractions, the petroleum fractions are mixed with theguanidine compound and reacted as described above. This process is alsoapplicable to the recovery and reclaiming of used crankcase oils. Insuch a process, the used oils are first filtered through a granularadsorbent to remove asphaltic and tarry materials, and then are treatedwith the guanidine compound for removal of acidic components. Thefinished petroleum products which are obtained in this manner have lowacid neutralization numbers, have increased resistance to oxidation andheat breakdown, and are more stable against color deterioration onextended storage. After addition of oxidation inhibitor and sludgedispersants, these reclaimed fractions are equal to or even better thanunused oils containing the same additives.

The following non-limiting examples are illustrative of the scope ofthis invention.

Example I A petroleum fraction of high acidity was pepared by dissolving33.1 g. of a commercial mixture of naphthenic acids (average molecularweight, 330) derived from petroleum (Sunaptic Acid B, manufactured bySun Oil Company) in 130.1 g. of 85 vis. neutral oil. The resultingsolution was dark in color and had an acid number of 33.4. A 31.0-ml.portion (27.4 g.) of the solution was mixed with 1.0 ml. (8.6 g., 0.075equivalent) of tetramethylguanidine and 40 ml. of methanol in a 100-ml.mixing graduate. The mixture was agitated and then allowed to settle for72 hours. At the end of this time, three phases had separated: an uppermethanol phase having a volume of 65 ml.; a middle oily phase having avolume of 25 ml.; and a lower phase having a volume of 1 ml., consistingessentially of tetramethylguanidine naphthenate. The oily phase whichwas recovered was considerably improved in color and was slightlyalkaline, apparently due to the presence of small amounts of dissolvedtetramethylgnanidine. This treatment resulted in the lowering of theacid number of the oil from 33.4 to or even slightly alkaline. Theresidual tetramethylguanidine present in the oil andtetramethylguanidine naphthenate which did not separate can be removed,if desired, by washing the oil with methanol.

The tetramethylguanidine naphthenate which is recovered is thetetramethylguanidine salt of the mixture of naphthenic acids which waspresent in the oil. Tetramethylguanidine naphthenate is slightly solublein oil and improves the wear characteristics of a lubricating oil. Also,the tetramethylguanidine naphthenate has surfactant properties and isuseiul as a detergent.

Example 11 A 20-ml. portion of the oil-acid mixture used in Example I(containing approximately 0.01 equivalent of acid) was shaken in a ml.mixing graduate with 50 ml. of a 1:1 methanol-water mixture containing,in suspension, approximately 0.08 equivalent of guanidine carbonate.After the mixture had settled for 72 hours, three phases had separated,as in Example I: 13 ml. of an upper, oily phase; 12.5 ml. of a middlephase, consisting of a concentrated solution of guanidine naphthenate;and 44.5 ml. of a lower, aqueous-alcohol phase. Acidity measurementsmade on the oily phase revealed that the acid number had been reducedfrom 33.4 to less than 0.1. The color of the oil phase was substantiallyimproved over that of the original oil-acid mixture.

Example 111 A lubricating oil extract (having an acid neutralizationnumber of 6.5), obtained by phenol extraction of a lubricating oilfraction, is treated in accordance with the subject invention. A 100-g.portion of this lubricating oil extract (from the manufacture of vis.neutral) is agitated for 30 minutes with a slurry consisting of 10 g.guanidine carbonate in 20 ml. of 50% aqueousmethanol, While thetemperature is gradually increased from room temperature to F. Themixture is allowed to settle for 16 hours and the oil phase is washedwith 50/50 aqueous-methanol. The oil phase which is recovered has anacid neutralization number of 0. The guanidine naphthenates whichseparate as a separate phase, and are removed with the aqueous-methanol,can be used in detergent compositions and as lubricating-oil additives.Also, the guanidine naphthenates can be washed with a strong acid, e.g.,hydrochloric acid, sulfuric acid, etc., to recover naphthenic acids.

Example IV A solution of 60 g. (Vs mol, /3 equivalent) of guanidinecarbonate in 200 ml. of water was prepared and mixed with 200 ml. ofmethanol to produce a slurry for treatment of an acidic oil fraction. Asolution consisting of 500 ml. (424 g.) of an oil consisting of 89.9%wt. of 85 vis. neutral oil and 10.1% Wt. of a mixture of commercialnaphthenic acids (Sunaptic Acid B) was mixed with 200 ml. of theguanidine carbonate slurry and charged to a 1-liter separatory funneland shaken vigorously. After standing several hours, two lower phasesseparated: an aqueous phase of about 100 ml. and a phase consisting of asolution of guanidine naphthenate in aqueous alcohol.

The oily phase which remained was then shaken vig orously with theremaining slurry (200 ml.) of guanidine carbonate in aqueous methanol.After settling for several hours, there was about 230 ml. of aqueousphase and about 25 ml. of a phase consisting of a concentrated solutionof guanidine naphthenate. Thev oily phase was filtered several timesthrough Reeve-Angel paper until clear (although substantially darkerthan the original neutral oil). The oil had an acid number less than0.05 and a nitrogen content of less than 0.03%. The acid number andnitrogen analysis indicated that substantially all of the naphthenicacids were removed and that guanidinium naphthenates were present in theoil in only a very small concentration.

The naphthenate and aqueous methanol phases recovered from the treatmentof the oil were mixed with water and benzene, and sodium chloride wasadded and shaken with the mixture. The guanidine naphthenate was thussalted out of the aqueous methanol and recovered as a benzene solution.The benzene phase was stripped with nitrogen under vacuum and guanidinenaphthenate was recovered as a jet-black, viscous liquid. The productweighed 54.7 g.; the theoretical yield of guanidine naphthenate wascalculated to be 55.2 g.

Example V Four hundred ml. (339 g.) of 10.1/89.9 naphthenic acid-neutraloil mixture (prepared in accordance with Example IV) was charged to a1-liter separatory funnel. One hundred ml. of methanol and 25 ml. (22.8g., 0.20 equivalent) of tetramethylguanidine were added and the mixtureshaken vigorously. After standing for several hours, two phasesseparated: an upper oily phase of 365 ml. and a lower methanol phase of155 ml. (very dark in color and consisting of excesstetramethylguanidine and its naphthenate salt). The oil phase wasfiltered twice through double thicknesses of Reeve-Angel paper, and wasfound to have an ASTM color of +2, a nitrogen content of 0.09%, a totalbase number of 1.6, and a strong base number of 0.4. These analysesindicated that some free tetramethylguanidine was present in the oiltogether with some tetramethylguanidine napthenate, but no freenaphthenic acid was present.

The methanol phase was treated with water, benzene, and sodium chloride(as in Example IV). The benzene phase was recovered and subjected tovacuum-nitrogen stripping, to produce a product consisting essentiallyof tetramethylguanidine naphthenate. The product recovered weighed 45.2g. as compared to a theoretical yield of 50.5 g. This product was inkyblack in color and only slightly less viscous than the product obtainedin the previous example.

The oil phases from Examples I, II, III, and IV, containing a smallamount of guanidine naphthenate or tetramethylguanidine naphthenate weretested for extreme pressure properties and resistance to oxidation.These oils were tested on a Shell Four-Ball Machine and found to producea wear scar about 5% smaller than that produced by the base oil and aweld point about kg. higher than for the base oil. This improvement inwear properties and weld point for the oil is obviously due to thepresence of a small concentration of guanidine naphthenate ortetramethylguanidine naphthenate in the oil. Portions of the oilcontaining guanidine naphthenate and tetramethylguanidine naphthenatewere subjected to the ASTM oxidation test, and the absorption of oxygenper hour per gram of oil Was substantially less for oils containing theguanidine naphthenate or tetramethylguanidine salt than for the baseoil.

While this invention is primarily concerned with the treatment of crudeoil and virgin oil fractions, it is also applicable to the reclamationof used oils. Used oils, such as crankcase oils, have been reclaimed byvarious methods, including distillation to remove crankcase dilution,percolation through adsorbents to remove asphaltic and tarry materials,and distillation over alkali to remove most of the organic acids. Wherethe oils contain a substantial amount of bright stock or othernon-distillable lubricating fractions, it has been diflicult to reclaimall of the oil satisfactorily. When bright stock is present in the oil,distillation in the presence of alkali to remove acids (produced bypartial oxidation of the oil during use) is not feasible. Thus, manyreclaimed oils have relatively high organic acidities and may givetrouble during use with certain types of bearings. In the followingexample it is seen how this process can be applied to the production ofreclaimed oils having low acid neutralization numbers and containingsubstantially no asphaltic or tarry material, regardless of whetherbright stock is present in the oil.

5 Example VI A used crankcase oil, black in color and having an acidneutralization number of 3.1 is percolated through fullers earth toremove asphaltic and tarry materials. The percolated oil is greenish-redin color and has an acid neutralization number of 0.7. A 1000-g. portionof the percolated oil is treated with 200 ml. of a slurry of 25 g. ofguanidine carbonate in 50/50 aqueous methanol at F. A mixture of oil andguanidine carbonate slurry is agitated for one hour and then allowed tosettle for 6 hours. The mixture settles into two phases and the oilphase is recovered and Washed with aqueous methanol. The treated oil iscompletely free of acid and has a very slight base number. Thisreclaimed oil has improved oxidation and color stability, and afteraddition of oxidation inhibitor and sludge dispersants to it, is equalto or even better than the unused oil containing the same oxidationinhibitor and sludge dispersants. The percolated crankcase oil cansimilarly be treated with tetramethylguanidine or other weak-acid saltsof guanidine, or of tetramethylguanidine or other alkyl-substitutedguanidines.

The used crankcase oil which is treated in accordance with this processcannot be converted to a product which is completely free of acid bymerely percolating it through fullers earth, or by distillation in thepresence of caustic, or by a combination of the two steps. This oil isonly about 40% distillable in the presence of caustic withoutsubstantial cracking.

While I have described my invention fully and completely with specialemphasis upon several preferred embodiments, I wish it to be understoodthat within the scope of the appended claims this invention may bepracticed otherwise than as specifically described herein.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as fol lows:

1. Naphthenate salts of compounds selected from the group consisting ofguanidine and alkyl-substituted guanidines.

2. Guanidine naphthenate.

3. Alkyl-substituted guanidine naphthenates.

4. Tetramethylguanidine naphthenate.

5. A solution of compounds defined in claim 1 in a petroleum fraction.

6. A method of preparing compounds as defined in claim 1 which comprisesmixing a guanidine compound selected from the group consisting ofguanidine, alkylsubstituted guanidines, and weak-acid salts thereof,with a petroleum fraction containing naphthenic acids at a temperaturesufficient to induce reaction and recovering the naphthenate salts thusformed.

7. A method in accordance with claim 6 in which the guanidine compoundis added in an alcohol and the product naphthenates are recovered as analcohol solution.

8. A method of refining a petroleum fraction containing a substantialamount of naphthenic acids which comprises mixing the fraction with aguanidine compound selected from the group consisting of guanidine,alkyl-substituted guanidines, and Weak-acid salts thereof in an amountat least stoichiometrically equivalent to the naphthenic acids presentat a temperature sufficient to induce reaction and neutralization ofsaid naphthenic acids, and extracting the resulting naphthenate saltsfrom the fraction.

9. A method in accordance with claim 8 in which the naphthenate saltsare extracted with a solvent selected from the group consisting of loweralcohols and lower alcohol-water mixtures.

10. A method in accordance with claim 9 in which the guanidine compoundis added to the petroleum fraction in admixture with the extractingsolvent and the resulting mixture subjected to agitation.

11. A method in accordance with claim 10 in which the 7 petroleumfraction is treated with a solution of tetramethylguanidine in methanol.

12. A method in accordance with claim 10 in which the petroleum fractionis treated with a slurry of guanidine carbonate in aqueous methanol.

13. In a method of reclaiming used crankcase oil in which the used oilis percolated through a granular adsorbent to remove asphalatic andtarry materials, the improvement Which comprises treating the percolatedoil in accordance with claim 8 to remove acidic impurities.

References Cited in the file of this patent UNITED STATES PATENTS1,281,354 Handy Oct. 15, 1918 2,580,881 Biswell Jan. 1, 1952 2,983,674Bauer May 9, 1961 OTHER REFERENCES Sachanen: The Chemical Constituentsof Petroleum, 0 1945, page 321, pub. Reinhold Pub. Corp, New York.

8. A METHOD OF REFINING A PETROLEUM FRACTION CONTAINING A SUBSTANTIALAMOUNT OF NAPHTHENIC ACIDS WHICH COMPRISES MIXING THE FRACTION WITH AGUANIDINE COMPOUND SELECTED FROM THE GROUP CONSISTING OF GUANIDINE,ALKYL-SUBSTITUTED GUANIDINES, AND WEAK-ACID SALTS THEREOF IN AN AMOUNTAT LEAST STOICHIOMETRICALLY EQUIVALENT TO THE NAPHTHENIC ACIDS PRESENTAT A TEMPERATURE SUFFICIENT TO INDUCE REACTION AND NEUTRALIZATION OFSAID NAPHTHENIC ACIDS, AND EXTRACTING THE RESULTING NAPHTHENATE SALTSFROM THE FRACTION.